The US has appealed against a WTO ruling that claimed American labelling rules for dolphin-friendly tuna were so tough that they broke global commerce regulations.

Washington opposes a WTO decision, made in September, that would allow importers, notably Mexico, to label tuna as 'dolphin-friendly' when fishermen corral dolphins (who eat tuna) to help them target these valuable fish. US authorities say this practice harms dolphins, although the Mexicans – and thus far – the WTO, disagree. 

The US Trade Representative office said: "Tuna products may not be labelled as 'dolphin-safe' if the tuna in those products is caught by intentionally encircling…dolphins with purse seine nets."